Air blowing Off Continuous While Driving XC-R Chassis

[Smoker]

As I drive down the road in my 2008 Forest River Berkshire (XC-R chassis - Freightliner Custom)it will sometimes (recently only) blow off air at about 10 times around / and seconds apart. The unit should always blow off some air while driving under normal conditions. However recently it will go about 10-15 times and within seconds apart. While driving and hearing the air blow off I do not seem to be losing air as the gauges are at normal (about 125 psi). I drain the tanks monthly. If the unit sits a week etc the tanks don’t lose much air. I'm thinking it might be the air dryer ? The maintenance on the (Haldex Pure Air Plus) it is every 36 months for a filter change. I have not done a filter change yet as my mech (retired diesel mechanic) said due to the low miles and my driving conditions etc it is still ok. He was planning to change it next spring. I think I will change it in short order and then see what conditions still exist.

Has anyone had this happen or heard of it?

Appreciate any input.

Thanks

Ron

[wolfe10]

Ron,

Sure sounds like a bad air dryer purge valve/check valve. Indeed, overhaul the dryer or replace with a factory reman dryer.

I would not drive it until this is fixed. Were it to stick open, you could loose air pressure.

Brett

[Smoker]

Ron,

Sure sounds like a bad air dryer purge valve/check valve. Indeed, overhaul the dryer or replace with a factory reman dryer.

I would not drive it until this is fixed. Were it to stick open, you could loose air pressure.

Brett

Thanks Brett.

I intend to have it looked at now.

Ron

[Smoker]

I spoke to Tom at Haldex in Kansas City MO.(the air dryer manufacturer). Tom claims I have either a bad compressor unloader and or a bad governor. He said that the air dryer is only doing what it should do when it rec air to it and that is to purge it off. He thinks it's working fine when I explained what it was doing. He said he would check these 2 items first. Does that make sense Brett? You mention a bad air dryer purge valve/check valve. Are you meaning the same as what Tom said? (I have a Haldex Purest Air Dryer OEM # N4253J.) Thanks...Ron

[sailwing]

If it is a bad D2 governor, know they are common and cheap, like $25. It is designed to unload at a certain pressure and allow the compressor to start again under lighter load. Easy to remove and replace when I did it, last month.

[Smoker]

If it is a bad D2 governor, know they are common and cheap, like $25. It is designed to unload at a certain pressure and allow the compressor to start again under lighter load. Easy to remove and replace when I did it, last month.

Thank Sailwing. Yes for for the cost would be a quick fix and or a part to rule out if it continues. Now a dumb question. Where is the D2 governor located ? I'm fairly sure I can change it once located. When having to crawl under the coach its hard to see things from having to look up. Would it be located on the dryer itself ? Thanks Ron.

[Smoker]

Ron,

Sure sounds like a bad air dryer purge valve/check valve. Indeed, overhaul the dryer or replace with a factory reman dryer.

I would not drive it until this is fixed. Were it to stick open, you could loose air pressure.

Brett

Problem fixed. It was a bad air dryer purge valve like you said. I ended called up Freighliner and hit the right person on the phone that day who basically told me what it was likely doing (two other tries had people on the phone saying other things as well). He gave me the part number and $15.00 later I'm back in business. The valve was about the size of my thumb and easy to change. Thanks for all you help. It was excellent to narrow in to my problem without costing me a arm and a leg. And to boot F/L even was going to as good will fix it but it would of cost more in fuel to drive it to a service center. ...Ron

[Krashpad]

I am having the same problem with my Freightliner chassis(09) Tiffin with the PURest air dryer. I actually had the problem on the road last month and a mobile repair guy changed out the purge valve, however it appears he changed it out with a valve for a different dryer and although it worked for a while it now is acting up again, this is how I discovered he used a purge valve rated at 150psi and the Freightliner guy said I need the 200 psi valve (size of a thumb) . So I am headed under the coach tomorrow to change it out. Any other tips before I head under?

I had one concern and that was whether to build up the airbags and raise the rear end up with jacks prior to going under(to get more clearance) but what about the air in the dryer prior to taking off the valve, do I bleed it off and how?

[wolfe10]

You can check with Freightliner-- many air systems have a check valve such that air would not escape when you remove the check valve.

BUT (yes, BIG BUT) it is a lot safer to release all air pressure before working on the air system. Use jack stands if, with the bags deflated you do not have room.

And before doing anything, I would check with the makers of your air dryer to confirm the part number of the proper valve.

Brett

[Krashpad]

Yes, I released all the air in the system, drew a little blood on the way out from the front after pulling the lanyards. That should of told me how things would go.

The wrong part that was in the Dryer was in "Very" tight. I actually began to strip the hex and stopped. I got another wrench and carefully tried again. I ended up stripping the bolt after getting half of the former part out (it was a 2 part piece). I had to go to the auto parts place and get a "stripped bolt" extractor tool. That worked.

Next I put in the new part (KN31529) which was verified by a FCCC tech to be the correct part. I also asked him as to what torque to install it and he said to tighten to between 144-192 in. lbs. of torque. So as I tightened this part at around 60 ft- Ibs. It broke right in half. Not kidding. Back to the parts store this time to get the extractor tool that goes inside the bolt (the last one fit over the bolt).

So if there was any good news at the end of the day ,I got that one out also without any (apparent) damage to the dryer and I will head out today to find another part and try again. I think Mr.fccc gave me the wrong torque because that certainly felt like too much.

[OkieDave]

If you were tightening the part with a regular foot pounds wrench then the correct torque should be about 15 Ft lbs. Yep, 60 would be a killer.

To convert foot pounds to inch pounds, multiply by 12.

To convert inch pounds to foot pounds, divide by 12.

[wolfe10]

Correct. If you torqued to 60 ft-lbs that is 720 in-lbs.

[Krashpad]

Yep, new part installed. Tested for leaks and operating as it should. What an experience and why would one chassis tech give me Inch Pounds and the part manufacturer give me foot pounds?

I'll never know but lesson learned once again.

Thanks for all the tips.

[wolfe10]

Both inch-lbs and ft-lbs are common measures of torque.

Inch-pounds being more common on low torque specs.

I have both inch-lb and ft-lb torque wrenches. The inch-lb is 3/8" drive, the ft-lb is 1/2" drive.

Brett

[tmmar]

Krashpad,

I saw your post detailing how the purge valve broke when you were installing it. Well, guess what. Mine broke off when I was trying to remove the old one. I am at the stage were there is half of the valve still in the air dryer. Did you do anything special when you removed the old valve? Did you use penetrating oil or heat when removing the old valve? It seems that it is extremely tight in the dryer and that there is some locktite on the threads. Did you remove the dryer from the coach to work on it or did you work on it while it was still in the coach?

Thanks for any tips you can give me on this.

Tom

[Krashpad]

Put it this way the old valve was indeed tight! As I mentioned I actually started to strip the Hex Bolt part So I got it out using a "Stripped Bolt Extractor"( fits over the top of the stripped bolt) I got from the auto parts store. So the next time after breaking the valve I had to go get an "Extractor tool" (that gets hammered into the inside of the broken valve) , also from the auto parts store. Both times used penetrating oil. Use an "adjustible wrench' or "Tap" wrench to work the broken valve out. The whole time I was working on the Dryer "ON" the coach. I did have the jacks down but only at ground contact and did not raise them up after discharging the air bags. Good luck, the Extractor tools worked as advertised and it was the first time I have had to use these kind of tools.

[tmmar]

Did you have to worry about any shavings getting in the dryer when using the easyout? Not sure what would happen if this occurred.

[mmiille]

One of the rear air bags on my mh isn't filling up after replacing the bad valve and element. I am guessing they aren't related, but you guys were very helpful in fixing my bad valve problem. Is the bag easy to fix? I don't hear air leaking anywhere.

Martin

2009 Damon Tuscany w/Freightliner chassis and cummins 360

[dickandlois]

Hi Martin,

Welcome to FMCA.

Right after the parts where changed did both air bags inflate? The air supply lines for the air bags is only a 1/4in. in size and is not a high volume line.

The next question is do your air gauges read normally? Thinking your Red gauge would be running on the low side if you have some kind of leak.

Freightliner uses one ride height control to control both rear airbags. So if one is inflating there is a plumbing issue or a hole in the new airbag and that is unlikely.

Martin, a little slow this AM. I see that you did not change the air bag as I reread your post, so it could have a hole. They dry out and start to crack around the bags at the fold point as they age. Not something most owners want to tackle.

Rich.

[mmiille]

Still looking but don't hear any leaks. Thinking the air line might be plugged. The other bag fills up fine. I will trace the line to see where it connects.

Both tanks are over 100 psi.

[tmumsey]

So, your air dryer pressure relief valve keeps popping off randomly on your diesel RV or truck equipped with air brakes. Or your air pressure is not consistent. Mine ranged randomly from 95psi to as high as 125psi. There are several problems which can cause this. The a bad relief valve, the governor on the air compressor being bad (Common problem. They are cheap so carry a spare) or clogged governor control lines.  But a  hidden problem could be inside the Haldex air dryer.  Especially if it is getting a little old. (Mine is 23 years old. Impressive it lasted that long. A shout out to Haldex!!)

I have the Haldex N50011h air dryer. Hidden inside the air dryer is a shuttle valve which provides control air to the governor. The shuttle o-ring or rubber washer degrade over time. My rubber washer was toast. Failure causes the governor to not cut out when it should and overpressure the system.  For this air dryer, the part number is Haldex DQ6031, Turbo Kit for Pure Air Plus (see pic). There are similar shuttles inside most air dryers as the dryer usually provides control air to the governor. You can replace the air dryer for about $350 or purchase the shuttle kit for about $30 (I found mine on eBAY). It is a pain to get to, but will fix the problem. To see the shuttle valve, remove the air dryer spin-on filter and internal screen . Look down the hole to see a a bit of the shuttle. To get to it, you have to remove the air line adaptors opposite both sides of the shuttle hole. There is a spring, so watch it as you remove the adaptors. Remove the screw and rubber washer out one side and the shuttle out of the other. Clean the hole thoroughly. Inspect the hole for excess corrosion or scratches. If that is bad, sorry you need a new air dryer. Lightly lube the hole. The rubber washer is screwed to the opposite end of the shuttle and must be inserted opposite the shuttle. That screw is painful to put in as you can't see it where it meets the end of the shuttle. It should slide easily back and forth about an inch when assembled correctly. Reassemble in reverse. Put the money you save in the gas tank and hit the road again. Good Luck!!!!

Edited March 5, 2021 by tmumsey

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